Our application will address the need for diagnostics to discriminate common flu-like pathogens from bioterrorist agents. Our approach is to use microarrays to detect changes in blood cell RNA within hours of exposure. Sets of genes will be identified that discriminate one pathogen from another, and these genes will be used to make a small microarray to further streamline diagnosis. Such an approach will eliminate the need to wait for symptoms or for pathogen replication. [unreadable] Within hours of exposure to a pathogen, white blood cells respond by altering their gene expression. RNA from white blood cells will be transcribed into cDNA and hybridized to standardized gene microarrays that monitor changes in cellular mRNA expression. Although the majority of the responses are non-specific (such as interferon responses to pathogen nucleic acid), an important subset is specific and potentially diagnostic for discriminating between exposure to one pathogen and another. Preliminary data demonstrate specific gene expression patterns in response to several bioterrorist agents. We will use cultured human lymphocytes: monocytes (4:1) to monitor mRNA responses to 4 different viruses causing flu-like symptoms (Influenza A, Parainfluenza 1, Rhinovirus, and Respiratory Syncytial virus). We will establish a database of gene expression responses that are diagnostic and specific for those viruses. These findings will be validated by comparison with gene expression in PBMC from human subjects. [unreadable] [unreadable]